$color:rgb(245, 245, 225);
.b1{
    width: 100px;
    height: 100px;
    background-color: $color;
}
$size:50;
@function fun($px:20px) {
    @return $size*$px;
}
.b2 {
    width: fun(1px);
}
@mixin myStyle($size){
    height:$size;
    background-color: blue;
}
.b3 {
    @include myStyle(100px);
    width: 20px;
}
